The present invention relates to door watershields that prevent water, sound, and dirt from entering into the vehicle passenger compartment.
Door watershields are made of a broad range of materials including stamped sheet metal, injection molded rigid polymer, and resilient closed cell foamed and non-foamed polymers. The watershields also may be combined with other acoustic materials within the trim panel to door cavity to provide sound attenuation in the vehicle passenger compartment.
Typically, prior door watershields were formed of a substantially solid non-porous sheet of non-water and non-air permeable polymeric material. Non-porous polymeric materials provide sound attenuation as a barrier by which reflects sound waves in direct proportion to their mass. However, a preferred sound attenuation method is by absorption, due to the lower mass or sound absorption materials. Sound absorption typically was provided by separate open cell foamed pads or fibrous pads fixed to selected portions of the polymeric sheet or trim panel. These absorbers were protected by the watershield from absorbing water.
It is known that typical acoustic absorber pad materials, such as open-cell foams and fibers, perform more effectively in response to an increase in thickness. However, it is believed that these absorbers can be further improved in sound absorption capability.
Combinations of polymeric sheets and fiber elements have also been used for various sound and water blocking areas of a vehicle, such as a dashboard pad in a vehicle passenger compartment. One such composition uses a polyethylene film and a lofted, non-woven microfiber pad sold commercially under the Thinsulate trademark by 3M.
It is also known that fabrics can be manufactured which are air permeable and non-water permeable for use in outdoor clothing, outdoor covers, etc
Such fabrics can be formed of a non-woven fabric or web in which a structure of individual fibers or threads are interlaid in an unidentifiable pattern. Non-woven fabrics or webs can be formed by a number of different processes, such as spunbonding and meltblowing. Spun bond fibers are small diameter, long strand length fibers, which are formed of extruded molten plastic material. Meltblown fibers can also be formed by extruding the molten plastic material through a die into a high velocity gas stream which attenuates the filaments and reduces their diameter. The meltblown fibers are then carried by the high velocity gas stream and deposited on a collecting surface so as to form a web of randomly dispersed meltblown fibers.
In a vehicle, it is important for occupant comfort that car component and exterior noise be attenuated, as much as possible, before entering the passenger compartment. Such noise spans a range of frequencies, such as 500-20,000 Hz, with engine, tire and road noise generally falling on the low end of the frequency spectrum in the 500-5,000 Hz frequency range and track squeal generally having substantially higher frequencies at the upper end of the defined frequency range.
When compared to more conventional methods of sound attenuation, it is preferable from a cost, weight and accosting performance perspective to provide an air permeable, water repellent, acoustic door watershield which is capable of blocking water and dirt ingress into a vehicle passenger cabin while at the same time attenuating noise over the broad frequency range of noise experienced in a vehicle. It would also be desirable to provide an air permeable, water repellent, acoustic door watershield in which the watershield can be easily conformed to vehicle door shapes and, further in which targeted acoustic performance and hydrophobicity can be optimized by selecting the air permeability of the door watershield.